Plate clamp



Aug. 27, 1929. J, R, BLM'NE 1,725,779

PLATE CLAMP Filed June .10, 1927 +5 @j 555x356 if Ja jim/22W:

Patented Aug. 27, 1929.

UNITED STATES PATENT OFFlCE.

JOSEPH R. BLAINE, OF OAK PARK, ILLINOIS, ASSIGNOR TO THE MIEIILEPRINTING PRESS n MANUFACTURING COMIANY, OF CHICAGO, ILLINOIS, ACORPORATION F ILLINOIS.

PLATE CLAMP.

Application led .Tune 10,

This invention relates to means for securing a flexible sheet to asupporting surface. It is more particularly adapted for positioning andholding a flexible printing plate or the like on a printing element of aprinting press.

In connection with certain types of printing presses, for example, Wherethe design or matter to be printed is provided on a metal or otherflexible sheet, such sheet must be securely clamped to and stretchedover a supporting member, such for example as a flat bed or as acylinder. rlhis is usually accomplished by means of one or more seriesof relatively movable clamping devices arranged in spaced relation onthe supporting member to engage opposite edges of the flexible sheet orplate and adapted to pull the latter taut over the supporting member.

For the purpose of accurately positioning a flexible printing plate orthe like on its supporting surface, it is desirable to mount the plateso that it can be shifted laterally of its supporting member, i. e.longitudinally, or axially if applied to a cylindrical support.

It is, therefore, the principal object of my invention to providesimple, reliable and efficient means whereby a flexible sheet such as aprinting plate or the like can be readily shifted on its supportingmember Without or edges of the sheet.

A further object of the invention resides` in the provision of simpleand practical means for shifting as a unit all of the clamping memberssecured to one edge of a clamped sheet.

Other objects of the invention will be apparent from the followingdescription and appended claims.

I have chosen to illustrate and describe a' preferred form of myinvention as applied to a lithographie or offset printing press.However, inasmuch as the invention is susceptible of embodiment invarious forms of construction and adapted for other uses Withoutdeparting from the spirit thereof, I 4do not Wish to limit the inventionto the particular form illustrated and described, but I intend to coverall possible modifications that may come Within the spirit and scope ofthe appended claims.

In the accompanying drawings,

1927. Serial No.-197,795.

Figure 1 is a cross-sectional view taken through a printing presscylinder to which my invention is applied, and showing more specificallythe general arrangement of the actual clamping means;

Figure 2 is a similar View of a printing press cylinder but illustratingthe scheme for shifting the clamping means illustrated in Figure 1;

Figure 3 is a partial view taken along a plane indicated by the line 3-3of Figure 1;

Figure 4 is a view of a detail;

Figure 5 is an elevation of a det-ail, taken along line 5 5 of Figure 1;and

Figure G is a cross-sectional view of a detail, taken along line 6 6 ofFigure 2.

' For the purpose of mounting the clamping and shifting means which formthe subject of my invention, the cylinder 10 is formed With a recessedportion or cavity 11 so as to provide a support 12 for said means. Theprinting plate 13 of the press is securely clamped and held in positionon the plate cylinder 10 by means of the clamping means as clearlyindicated in Figure 1. Said means comprises a block 14, Which forms thelovver clamping member and Which is adapted to slide over the surface 15of thesupport 12 by turning the threaded tensioning spindle 16 which isjournaled at 17 Wit-hin a horiv Zontal bearing slot 46 provided in thebracket detaching the clamping means from the edge 18, see Figure 5.Said bracket is preferably secured to the support 12 by means of one ormore bolts 19. Tle inner end of the spindle 16 is formed With a trunnionWhich is journaled at 20 Within a laterally shiftable bar 21. For thepurpose of providing a stop for the edge of the printing plate or thelike, the block or lower clamping member 14 is preferably provided ateach end with projections 22 as shown in Figures 1 and 3.

The upper clamping member 23 which cooperates With the block14 ismounted on a shaft 24, which is loosely supported Within rearwardlyextending portions of the block 14 and held in position by Cotter pins25. The clamping member 23 is provided With an elongated slot 26 whichreceives the locking bolt 27. The latter is threaded at 28 into theblock 14 and is formed with a collar 29 which bears against an abutmentsurface on the clamping member 23. The block 14 is forced against thecollar 29 by means of an expansion coil spring 32 housed Within recessesand 31 which are provided in the block 14 and in the member 23respectively so as to separate the clamping jaw of said member from thejaw portion of the block 14 when the bolt 27 is loosened, In order tomove the block 14, together with its associated parts, over thesupporting surface 15, either for the purpose of tensioning or releasingthe tension of the flexible sheet 13, a wheel 33, formed with pin holes34, is preferably mounted on said spindle adjacent the outer endthereof.

Referring to Figure 2, the means for laterally shifting the bar 21, andtherewith the clamping members 14 and 23 and associated parts, comprisesa shifting spindle formed at its outer end with a journal 36 mountedwithin the bracket 37 which is secured to the support 12 by means ofbolts 38. The inner end of the shifting spindle 35 is supported by meansof a trunnion 39 journaled at 40 within the cylinder wall. The shiftingspindle is formed with an excentric 41 which engages within a verticallydisposed cam slot 42 provided in the shifting bar 21.

It will be evident upon inspection of Figures 2 and 3 that when thespindle 35 is turned, for example in an anti-clockwise direction, bymeans of a` pin wrench applied to the pin hole 43, the shifting bar 21will be shifted to the right or vice versa. Preferably, the bar 21 issupported and guided by means of shoulder bolts 44 which pass throughhorizontal slots 45 in said bar.

Inasmuch as the threaded tensioning` spindle 16 at each unit of clampingmembers, such as illustrated in Figure 3 and of which there may be anydesirable number, is journaled at its inner end Within the bore 2O ofthe shifting bar 21, while its outer end is supported wit-hin theelongated slot 46 of the bracket 18, it will follow the shiftingmovement of said bar, therefore the clamping members will slide over thesurface 15 in whichever direction the bar 21 is shifted, and alignthemselves automatically.

It will be understood of course that prior to shifting the bar 21 it isessential to loosen up each tensioning shaft 16 to some extent so as toreduce the friction between the flexible sheet and its supporting`member.

It has been suggested to provide antifriction means between thetensioning screw of a plate clamp and its bearing surface on the platesupporting member, so that the plate may be shifted without previouslyreleasing its tension. It is obvious, however, that such devices areimpractical, particularly when applied to convex supports, and that inorder'to avoid any distortion of a printing plate or the like it isnecessary to relax the tension of such plate.

I claim:

1. The combination with a flexible sheet supporting element, of meansfor securing the flexible sheet thereto, comprising a series of holdingelements adapted to engage said sheet, and means operatively connectedwith each one of said holding elements for positively shifting saidelements, and the flexible sheet laterally without the necessity ofreleasing the holding elements therefrom.

2. The combination with a flexible sheet supporting element, of meansfor securing the flexible sheet thereto, comprising a series of holdingelement-s adapted to engage said sheet, and a shifting bar arranged toengage each one of said holding elements for shifting the latter as aunit relatively to said supporting element, without the necessity ofreleasing the holding elements from said flexible sheet.

3. The combination with a flexible sheet supporting element, of meansfor securing the flexible sheet thereto, comprising a series of holdingelements adapted to engage said sheet, and a cam actuated shifting bararranged to engage each one of said holding elements for shifting thelatter as a unit relatively to said supporting element, without thenecessity of releasing the holding elements from said flexible sheet.

4. The combination with a supporting element for a printing plate or thelike, of means for holding the printing plate or the like rigid on saidelement, comprising a series of independently operable clamping membersadapted to engage and grip the edge of said printing. plate or the like,and means arranged to engage each one of said clamping members forshifting them as a unit longitudinally of said supporting element.

5. The combination with a flexible sheet supporting element of aprinting press or the like, of means for securing the flexible sheet tosaid element, comprising series of independently operable shiftingclamps adapted to clamp opposite edges of said sheet, and means arrangedto engage each one of a series of clamps for shifting the clamps on eachedge as a unit relatively to the supporting element, for the purpose ofpositioning the sheet thereon. 6. In combination with a flexible sheetsupporting element, an adjustable member associated therewith, ashifting spindle for operating said member, a series of sheet holdingmembers engaged by and mounted for unit adjustment with said adjustablemember, and means for automatically align- Iing said holding members asthey are being adjusted.

7. In combination with a flexible sheet supporting element, a camactuated, adjustable shifting bar associated therewith, a shiftingspindle for operating said bar, a series of sheet holding membersengaged by and mounted for unit adjustment with said adjustable member,and means for automatically aligning said holding members as they arebeing adjusted.

8. In combination with a printing plate or the like supporting element,a ylaterally shiitable member associated therewith, a shitting spindlefor operating said member, a series of independently adjustable holdingmembers engaged by and mounted for unit adjustment with said shiftablemember, and means for aut-omatically aligning said holding members asthey are being adjusted.

9. In combination with aprinting plate or the like supporting elements,a manually adjustable bar associated therewith, a shifting spindle foroperating said bar, a series ot' independently adjustable clampingmembers engaged by and mounted for unit adjustment with said adjustablebar, and means for automatically aligning said holding members as theyare being adjusted.

l0. In combination with a flexible sheet supporting element, anadjustable member associated therewith, a. series of sheet holdingmembers mounted for unit adjustment with said adjustable member,tensioning means operatively engaging said sheet holding members. andmeans for aligning said tensioning means and holding members.

l1. In combination with ay iiexible sheet supporting element, alaterally adjustable member associated therewith, a series ofindependently adjustable sheet holding members mounted for unitadjustment with said laterally adjustable member, tensioning meansoperatively engaging said sheet holding members, and means forsimultaneously aligning said tensioning means and holding members duringthe lateral adjustment of the latter.

l2. In combination with a supporting element for a printing plate or thelike, a cam actuated, laterally shiftable member associated therewith, aseries' of independently adjustable clamping members mounted for unitadjustment with said cam actuated member, tensioning means operativelyengaging said clamping members, and selfaligning means for saidtensioning means and clamping members.

18. A shifting plate clamp for positioningk a printing plate on acylinder of a printing press, comprising a plurality of cooperatingclamping members arrange-d in pairs at intervals along an edge of theprinting plate, means for independently securing each pair of clampingmembers to said plate, tensioning means operative to stretch said platetaut over the cylinder, means comprising a shifting bar mounted on thecylinder wall and supporting said tensioning means, means operative toshift said bar and thereby move the clamping members as a unitlongitudinally otthe cylinder, and means for aligning said tensioningmeans and clamping member during the longitudinal movement of thelatter` 14. A shifting plate clamp for positioning a printing plate on acylinder ot a printing press, comprising a plurality oi cooperatingclamping members arranged in pairs at intervals along an edge of theprinting plate, means for independently securing each pair et clampingmembers to said plate, means operative tostretch said plate taut overthe the cylinder, a shifting bar mounted on the cylinder wall andsupporting said last referred to means, means operative toy shift saidbar, together with the means supported thereby, relatively to thecylinder and comprising a shifting spindle formed with an eXcentricportion which engages within a cam slot in said bar.

Signed at Chicago, Illinois, this 6th day of June, 1927.

JOSEPH R. BLAINE.

